There are electrical apparatus cases having a cable or a line cord (hereafter, generically called a cable). An example of an electrical apparatus having such a case is an AC adapter. An AC adapter is an apparatus configured to convert AC power supplied as a commercial power source into DC power and supplying the DC power to an electrical device. In the inner space of the case of the AC adapter, a power source board functioning to convert the AC power to a DC current having a predetermined voltage is provided. A pair of tap edges is provided on a side wall of the case to penetrate through the side wall of the case so that a power plug is formed. An end of each tap edge protruding toward the inner space of the case is electrically connected to the power source board so that AC power of a commercial power source can be supplied to the power source board by inserting the other end of each tap edge into a wall socket.
To a DC output terminal of the power source board, a cable for supplying DC power generated by the power source board to an electronic device is connected. In another side wall of the case, a through hole for passing the cable therethrough is formed. The cable is inserted into the through hole through a bushing formed integrally on an outer circumferential part of the cable. With this structure, the cable extending from the through hole to the outside of the case is prevented from being broken by bending at a proximal end part of the cable. The inner space of the case is filled with resin such that the entire of the power source board is covered with resin. Consequently, the power source board is waterproofed. In general, the case includes an upper case member and a lower case member. After integrating the upper case member and the lower case member by ultrasonic welding, the inner space is filled with resin so that the power source board is made waterproof.
The conventional waterproof case has the above mentioned general structure, and therefore the waterproof property of the case is maintained. However, the conventional waterproof case has a drawback that the case is not able to completely prevent moisture from entering the case via the through hole where the cable is drawn from the case.
In 2004-265748A (Japanese Patent Provisional Publication), the assignee of this application discloses a waterproof structure which is configured such that an injection region is formed on a side wall of a case to have an inner space so that the waterproof property of a through hole for drawing of the cable is enhanced, the through hole is formed to penetrate the injection region from the outside to the inside of the case, resin is injected to cover the cable placed to penetrate the through hole from the outside to the inside of the case at a part of the cable passing the injection region so that the waterproof property of the part of the cable is secured.
If the waterproof structure is configured to have a bushing to prevent breaking of the cable due to bending at the cable drawing part, a problem, that moisture can not be completely prevented from entering the case even if the injection region is filled with resin to secure the waterproof property, arises.
The reason is that although the bushing is formed integrally with an outer sheath of the cable by resin molding, complete integration is impossible and production of a gap between the bushing and the cable can not be avoided because the outer sheath of the cable and the bushing are molded separately. If such a gap is produced, moisture may enter the inside of the case through the gap between an inner circumferential part of the bushing and the outer circumferential part of the cable.